Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover the read-only/safe profile, and the description adds real behavioral context: results include planned targets alongside actuals, and volume in kg is always 0 for bodyweight exercises (a genuinely useful interpretation caveat). It does not discuss limits/defaults, though the schema handles that.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three front-loaded sentences that lead with what is returned before moving to use cases. Dense with quoted phrasing but every clause carries information; nothing is filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With annotations covering safety and an output schema covering return structure, the remaining burden is purpose and usage, both addressed. The description is self-sufficient for a zero-required-parameter read tool, though it never contrasts itself with the nearest siblings.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3; the schema already explains limit, workout_id, exercise_id, and exercise_name. The description only echoes the exercise_name use case (comparing a movement across recent sessions), adding marginal meaning beyond the structured field.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific resource and scope (completed sets, reps, weight, planned targets from past sessions) in vivid terms rather than restating the name. It distinguishes itself from progression/target-oriented siblings implicitly by emphasizing 'what the user ACTUALLY did', though it never names a sibling it must be told apart from.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives concrete scenarios — 'how did I do?', coaching progressive overload, bodyweight work — and tells the agent to narrow by exercise_name for cross-session comparison. There is no explicit exclusion or named alternative (e.g. get_exercise_progression), so the routing guidance is contextual rather than decisive.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.